The present invention generally relates to a safety switch, and in particular to a safety switch of a type having a spring-biased locking pin which can be displaced axially inside a switch housing by a lifting magnet in opposition to the biasing force of the spring into a position for releasing a switching element.
Various designs of safety switches with lifting magnets are known in the art. In general, the safety switch of this type is forced into the off-position when an actuating element is pulled out, whereby a compression spring which acts on the locking pin pushes the locking pin into a blocking position. The switching element which is typically constructed in the form of a switch wheel can be released by energizing the lifting magnet so that the armature thereof is displaced against the bias force of the compression spring to thereby move the locking pin into the release position.
In conventional safety switches, the lifting magnet is energized, i.e. current flows through the windings of the lifting magnet, until the locking pin moves again into the blocking position. The lifting magnet must be so dimensioned as to be able to generate the lifting force required to unlatch the locking pin. The lifting force, however, is significantly greater, typically about forty times greater, than the holding force required to retain the locking pin in the release position. A drawback of conventional safety switches is their substantial power consumption, and the significant heat build-up as a consequence of the high current flow.